Tom's Blog

Monday, August 17, 2009

Original vegetation map from the surveyor's records

The best data on the original vegetation of Wisconsin come from the Public Land Survey records done in the 1830s before the state had been settled. These data have been used in the past in a qualitative way by John Curtis, and later by Robert Finley to create a map of the whole state. Although the Finley map was a huge effort and has been a very useful tool for plant ecologists, it has now been superceded by a version of the map created by Forestry Professor David Mladenoff's group using GIS technology. This new version is available as an insert in Wisconsin Natural Resources Magazine and as a PDF version at the following link: This version has the advantage that it can be enlarged on the computer screen so that any small area of the state can be analyzed in detail.

I have been examining the Mladenoff map for distribution of oak savannas in southwestern Wisconsin, including the area in western Dane County that has Pleasant Valley Conservancy. Quantitatively southwestern Wisconsin was oak savanna, with rather small amounts of prairie. Because the land surveyors were required to record the species of trees near each survey point, Mladenoff's map gives the dominant tree species in each section. Two oak species were most often cited, bur (Quercus macrocarpa) and white (Quercus alba), with bur oak predominant. In the area of Dane County west of Madison, greater than 50% of the sections had bur oak as the main tree. Bur oak was also the principal tree throughout most of southern Wisconsin, in addition to a wide zone extending from Madison up to the west side of Lake Winnebago. (On the east side of Lake Winnebago, the vegetation was beech/maple woods rather than oak savanna.)

Since all the surveyor's records had to be computerized, the Mladenoff map represents a huge amount of work. We are so fortunate to have this valuable tool!


Blogger Scott said...

Very helpful Tom. I was struggling to fight my way through the original handwriting in the documents online. This link is great!

August 21, 2009 at 9:42 AM  

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